Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 24, 2013
Publication Date: March 1, 2014
Citation: Gast, R.K., Guraya, R., Jones, D.R., Anderson, K. 2014. Contamination of eggs by Salmonella Enteritidis in experimentally infected laying hens housed in conventional or enriched cages. Poultry Science. 93:728-733. Interpretive Summary: Internally contaminated eggs have been implicated in outbreaks of human illness caused by Salmonella Enteritidis more than any other food source. This pathogen is deposited inside eggs when infections of laying hens spread to the reproductive organs where eggs are formed. In recent years, considerable international attention has focused on the animal welfare and food safety consequences of different types of laying flock housing systems. In the present study, two different types of housing (conventional and enriched cages) were evaluated for their effects on egg contamination by laying hens infected with S. Enteritidis. Enriched cages are colony-type units providing greater floor space per bird with perches and enclosed nesting areas. After groups of laying hens were housed in each cage system and infected by oral inoculation, eggs were collected for several weeks and tested for S. Enteritidis contamination of their interior contents. No significant differences between the two housing systems were observed in the frequency of S. Enteritidis isolation from eggs. The public health consequences of housing systems for egg-laying flocks are related to both how long S. Enteritidis persists in the environment and how often infected hens lay contaminated eggs.
Technical Abstract: Both epidemiologic analyses and active disease surveillance confirm an ongoing strong association between human salmonellosis and the prevalence of Salmonella Enteritidis in commercial egg flocks. The majority of human illnesses caused by this pathogen are attributed to the consumption of contaminated eggs. Animal welfare concerns have increasingly influenced commercial poultry production practices in recent years, but the food safety implications of different housing systems for egg-laying hens are not definitively understood. The present study assessed the effects of two different housing systems (conventional cages and colony cages enriched with perching and nesting areas) on the frequency of S. Enteritidis contamination inside eggs laid by experimentally infected laying hens. In each of two trials, groups of laying hens housed in each cage system were orally inoculated with doses of 1.0 × 108 cfu of S. Enteritidis. All eggs laid between 5 and 25 d post-inoculation were collected and cultured to detect internal contamination with S. Enteritidis. For both trials combined, S. Enteritidis was recovered from 3.97% of eggs laid by hens in conventional cages and 3.58% of eggs laid by hens in enriched cages. No significant differences (P > 0.05) in the frequency of egg contamination were observed between the two housing systems.